Light emitting device and manufacturing method thereof

ABSTRACT

A light emitting device includes a first light transmissive supportive substrate having a first light transmissive insulator and a conductive circuitry layer provided on a surface of the first light transmissive insulator, a second light transmissive supportive substrate having a second light transmissive insulator and disposed in such a way that a surface of the second light transmissive insulator faces the conductive circuitry layer and so as to have a predetermined gap from the first light transmissive supportive substrate, a light emitting diode having a main body, and first and second electrodes provided on a surface of the main body and electrically connected to the conductive circuitry layer via a conductive bump, and laid out between the first and second light transmissive supportive substrates, and a third light transmissive insulator embedded in a space between the first light transmissive supportive substrate and the second light transmissive supportive substrate.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is continuation of International Application No.PCT/JP2014/005999, filed on Dec. 1, 2014, which is based upon and claimsthe benefit of priority from the prior Japanese Patent Applications No.2013-249453 and No. 2013-249454 filed on Dec. 2, 2013. The entirespecifications, claims, and drawings of Japanese Patent Applications No.2013-249453 and No. 2013-249454 are herein incorporated in thisspecification by reference.

FIELD

Embodiments of the present disclosure relate to a light emitting deviceand a manufacturing method thereof.

BACKGROUND

Light emitting devices including Light Emitting Diodes (LEDs) are widelyapplied to display devices indicator lamps, various switches, signalingdevices, and optical devices like general lighting instrument forindoor, outdoor, stationary and moving locations, etc. In such lightemitting devices that include LEDs, a light transmissive light emittingdevice which has a plurality of LEDs laid out between two lighttransmissive substrates has been known as a device suitable for displaydevices and indication lamps, etc., that display various characterstrings, geometric figures and patterns.

By applying a flexible substrate, etc., formed of a light transmissiveresin as the light transmissive substrate, a constraint to an attachmentplane for the light emitting device as the display device, theindication lamp, etc., is eased. This improves the convenience andapplicability of the light transmissive light emitting device.

The light transmissive light emitting device includes, for example, afirst light transmissive insulation substrate that has a firstconductive circuitry layer, a second light transmissive insulationsubstrate that has a second conductive circuitry layer, and, a pluralityof LED chips laid out therebetween. The plurality of LED chips eachincludes an electrode pair, and such electrode pair is electricallyconnected to the respective first and second conductive circuitrylayers. A space between the first light transmissive insulationsubstrate and the second light transmissive insulation substrateproduced by the plurality of LED chips laid out with a certain clearanceis filled with a light transmissive insulator formed of a lighttransmissive resin, etc., which has the electrical insulation propertyand the flexibility. In other words, the LED chips are laid out in athrough-hole formed in the light transmissive insulator.

As for the electrical connection between the electrode of the LED chipand the conductive circuitry layer in the above-explained lighttransmissive light emitting device, for example, thermal compressionbonding is typically applied to a laminated body that includes the firstlight transmissive insulation substrate, the light transmissiveinsulation resin sheet which has the through-hole in which the LED chipsare laid out, and the second light transmissive insulation substrate. Inthis case, by designing the thickness of the light transmissiveinsulation resin sheet (thickness of light transmissive insulator)having undergone the thermal compression bonding to be thinner than thatof the LED chip, the conductive circuitry layer is depressed against theelectrode of the LED chip so as to be in contact therewith. Theelectrode of the LED chip and the conductive circuitry layer may bebonded by a conductive adhesive. In addition, a technology of providinga hot-melt adhesive sheet that fastens the LED chips between the upperand lower insulation substrates each including the conductive circuitrylayer, performing thermal compression bonding thereto to embed the LEDchips in the adhesive sheet, thereby simultaneously accomplishing thebonding between the upper and lower insulation substrates and theelectrical connection between the electrode of the LED chip and theconductive circuitry layer has been proposed.

In any cases, however, the electrical connection between the conductivecircuitry layer and the electrode, and the reliability thereof are notsufficiently ensured. Therefore, there is a need to improve thoseproperties.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an exemplary cross-sectional view illustrating a schematicstructure of a light emitting device according to a first embodiment;

FIG. 2 is a cross-sectional view illustrating a part of the lightemitting device in an enlarged manner;

FIG. 3 is a plan view for explaining an example connection according toan embodiment;

FIG. 4A is a diagram for explaining a manufacturing method of the lightemitting device according to the first embodiment;

FIG. 4B is a diagram for explaining a manufacturing method of the lightemitting device according to the first embodiment;

FIG. 4C is a diagram for explaining a manufacturing method of the lightemitting device according to the first embodiment;

FIG. 4D is a diagram for explaining a manufacturing method of the lightemitting device according to the first embodiment;

FIG. 5 is an exemplary diagram for a bump (ball) shape prior to arounding process;

FIG. 6A is a diagram for explaining the rounding process using a jig;

FIG. 6B is a diagram for explaining the rounding process using a jig;

FIG. 6C is a diagram for explaining the rounding process using a jig;

FIG. 7A is a diagram for explaining a rounding process by a press workapplied to a resin sheet;

FIG. 7B is a diagram for explaining the rounding process by a press workapplied to a resin sheet;

FIG. 7C is a diagram for explaining the rounding process by a press workapplied to a resin sheet;

FIG. 8A is a diagram for explaining a layout of LED chips before andafter a press work;

FIG. 8B is a diagram for explaining a layout of LED chips before andafter a press work;

FIG. 9 is an exemplary cross-sectional view illustrating a schematicstructure of a light emitting device according to a second embodiment;

FIG. 10 is a cross-sectional view illustrating a part of the lightemitting device in an enlarged manner;

FIG. 11A is a diagram for explaining a manufacturing method of the lightemitting device according to the second embodiment;

FIG. 11B is a diagram for explaining a manufacturing method of the lightemitting device according to the second embodiment;

FIG. 11C is a diagram for explaining a manufacturing method of the lightemitting device according to the second embodiment;

FIG. 11D is a diagram for explaining a manufacturing method of the lightemitting device according to the second embodiment;

FIG. 12A is a diagram for explaining a layout of LED chips before andafter a press work;

FIG. 12B is a diagram for explaining a layout of LED chips before andafter a press work;

FIG. 13 is a diagram illustrating a light emitting diode, a lighttransmissive insulator, a conductive circuitry layer, and a lighttransmissive insulation substrate located around the light emittingdiode; and

FIG. 14 is a diagram illustrating a conductive bump formed on anelectrode of a light emitting diode in an enlarged manner.

DESCRIPTION OF EMBODIMENTS

A light emitting device according to the present disclosure includes:

a first light transmissive supportive substrate that includes a firstlight transmissive insulator and a conductive circuitry layer providedon a surface of the first light transmissive insulator;

a second light transmissive supportive substrate which includes a secondlight transmissive insulator, and which is disposed in such a way that asurface of the second light transmissive insulator faces the conductivecircuitry layer and so as to have a predetermined gap from the firstlight transmissive supportive substrate;

a light emitting diode which includes a light emitting diode main body,and first and second electrodes provided on a surface of the lightemitting diode main body and electrically connected to the conductivecircuitry layer via a conductive bump, and which is laid out between thefirst light transmissive supportive substrate and the second lighttransmissive supportive substrate; and

a third light transmissive insulator embedded in a space between thefirst light transmissive supportive substrate and the second lighttransmissive supportive substrate.

[First Embodiment]

A light emitting device according to a first embodiment of the presentdisclosure will be explained with reference to the figures. FIG. 1 is anexemplary cross-sectional view illustrating a schematic structure of alight emitting device 1 according to this embodiment. In addition, FIG.2 is a cross-sectional view illustrating a part of the light emittingdevice 1 illustrated in FIG. 1 in an enlarged view.

As illustrated in FIG. 1, the light emitting device 1 roughly includes alight transmissive supportive substrate 2, a light transmissivesupportive substrate 3, a light emitting diode 22, and a lighttransmissive insulator 13.

The light transmissive supportive substrate 2 includes a lighttransmissive insulator 4, and a conductive circuitry layer 5 provided ona surface of the light transmissive insulator 4. The conductivecircuitry layer 5 is provided on only the surface of the lighttransmissive insulator 4 that constructs the light transmissivesupportive substrate 2.

The light transmissive supportive substrate 3 includes a lighttransmissive insulator 6, and is disposed in such a way that a surfaceof the light transmissive insulator 6 faces the conductive circuitrylayer 5 with a predetermined gap. That is, the light transmissivesupportive substrate 3 itself has no conductive circuitry layer.

The light emitting diode 22 includes semiconductor layers formed on aninsulation substrate or a semiconductor substrate, and includes alight-emitting-diode main body 27, and electrodes 28, 29 which areprovided on a surface of the light-emitting-diode main body 27, andwhich are electrically connected to the conductive circuitry layer 5.The light emitting diode 22 is laid out between the light transmissivesupportive substrate 2 and the light transmissive supportive substrate3. The plurality of light-emitting-diode main bodies 27 are laid outwith a predetermined clearance. A minimum distance d between theadjoining light-emitting-diode main bodies 27 is not limited to anyparticular value, but the present disclosure is particularly suitablefor high-density packaging that has the minimum distance d which becomesequal to or smaller than 1500 μm.

In addition, the number of laid-out light-emitting-diode main bodies 27can be determined as needed in accordance with the specifications of thelight emitting device 1 (e.g., external dimension light emitting area).

As illustrated in, for example, FIG. 2, the light emitting diode 22includes an N-type semiconductor layer (e.g., n-GaN layer) 24, an activelayer (e.g., InGaN layer) 25. and a P-type semiconductor layer (e.g.,p-GaN layer) 26 formed on an insulation substrate 23 like a lighttransmissive sapphire substrate in this order. Note that the layoutpositions of the N-type semiconductor layer and P-type semiconductorlayer may be reversed. In this embodiment, a single-sided electrodestructure in which the electrodes 28, 29 are provided at thelight-emitting-surface side of the light-emitting-diode main body 27 isadopted. In addition, the single-sided electrode structure is applicableto the light emitting diode that has a semiconductor layer formed on asemiconductor substrate.

The electrodes 28, 29 of the light emitting diode 22 are electricallyconnected to the conductive circuitry layer 5 of the light transmissivesupportive substrate 2. The electrodes 28, 29 are each a pad electrodeformed of a material that is an alloy containing Au (gold).

As illustrated in FIG. 2, the electrode 28 contacts the conductivecircuitry layer 5 via a conductive bump 30, thereby being electricallyconnected to the conductive circuitry layer 5. The electrode 29 contactsthe conductive circuitry layer 5 via the conductive bump 30, therebybeing electrically connected to the conductive circuitry layer 5.

Example materials for the conductive bump 30 are gold, an Au—Sn alloy,silver, copper, nickel, an alloy of other metals, a mixture, an eutecticmaterial, an amorphous material, and may be a solder, an eutecticsolder, a mixture of metal micro particle with a resin, and ananisotropy conductive film, etc. In addition, the conductive bump 30 maybe formed by wire bumping using a wire bonder, electrolytic plating,non-electrolytic plating, inkjet printing and calcining of an inkcontaining metal micro particle, printing of a paste containing metalmicro particle, coating ball mounting, pellet mounting, vapor depositionsputtering, etc.

It is preferable that the melting-point temperature of the conductivebump 30 should be equal to or higher than 180° C., and more preferably,equal to or higher than 200° C. The practical upper limit should beequal to or lower than 1100° C. When the melting-point temperature ofthe conductive bump 30 is lower than 180° C., in a vacuum thermalpressing process in the manufacturing process of the light emittingdevice, the conductive bump 30 largely becomes out of shape, and thusthe sufficient thickness is not ensured or the bump spreads beyond theelectrode, thereby decreasing the light intensity of the LED, etc.

The melting-point temperature of the conductive bump 30 is, for example,a melting-point temperature value measured using a sample ofsubstantially 10 mg at a temperature rise rate of 5° C./min using aDSC-60 differential scanning calorimeter made by SHIMADZU Corporation,and when a solidus temperature and a liquidus temperature differ fromeach other, is a value of the solidus temperature.

A dynamic hardness DHV of the conductive bump 30 is equal to or largerthan 3 and equal to or smaller than 150, and preferably, equal to orlarger than 5 and equal to or smaller than 100, and more preferably,equal to or larger than 5 and equal to or smaller than 50. When thedynamic hardness DHV of the conductive bump 30 is less than 3, in avacuum thermal pressing process in the manufacturing process of thelight emitting device, the conductive bump 30 largely becomes out ofshape, and thus the sufficient thickness is not ensured. In addition,the bump spreads beyond the electrode, thereby decreasing the lightintensity of the LED, etc. Conversely, when the dynamic hardness DHV ofthe conductive bump 30 exceeds 150, in a vacuum thermal pressing processin the manufacturing process of the light emitting device, theconductive bump 30 deforms the light transmissive supportive substrate2, resulting in a poor visual inspection result and a poor connection,which is not suitable.

The dynamic hardness DHV of the conductive bump 30 is obtained by, forexample, a test at a temperature of 20° C. using a SHIMADZU dynamicultrafine hardness gauge made by SHIMADZU Corporation. In such a test, adiamond square pyramid indenter (Vickers indenter) with an angle betweenopposite surfaces that is 136 degrees is pushed in the conductive bump30 at a load speed of 0.0948 mN/sec. Next, a test force (P/mN) when thepush-in depth of the indenter reaches 0.5 μm is substituted in thefollowing formula.DHV=3.8584P/D2=15.4336P

It is preferable that the height of the conductive bump 30 should beequal to or larger than 5 μm and equal to or smaller than 50 μm, andmore preferably, equal to or larger than 10 μm and equal to or smallerthan 30 μm. When the height of the conductive bump 30 is less than 5 μm,a short-circuit prevention effect between the conductive circuitry layerand the P-type semiconductor layer or between the conductive circuitrylayer and the N-type semiconductor layer becomes insufficient, which isnot suitable. Conversely, when the height exceeds 50 μm, in a vacuumthermal pressing process in the manufacturing process of the lightemitting device, the conductive bump 30 deforms the light transmissivesupportive substrate 2, resulting in a poor visual inspection result anda poor connection, which is not suitable.

In addition, it is preferable that a contact area between the electrodeof the light-emitting-diode main body 27 and the conductive bump 30should be equal to or larger than 100 μm² and equal to or smaller than15000 μm², more specifically, equal to or larger than 400 μm² and equalto or smaller than 8000 μm². Each dimension is a measured value under astable environment in which a room temperature and the temperature of ameasurement object are 20° C.±2° C.

According to the light emitting device of this embodiment, theelectrodes 28, 29 of the light-emitting-diode main body 27 and theconductive circuitry layer 5 of the light transmissive supportivesubstrate 2 are connected by vacuum thermal pressing using theconductive bump 30. Hence, at the time of vacuum thermal pressing, theconductive bump 30 is electrically connected to the electrode of thelight emitting diode 22 with a part of such a bump not being melted.Accordingly, it is preferable that a contact angle between the electrodesurface of the light-emitting-diode main body 27 and the conductive bump30 should be equal to or smaller than, for example, 135 degrees.

The light emitting diode 22 emits light by a DC voltage applied via theelectrodes 28, 29. When, for example, the light emitting device 1includes the seven light-emitting-diode main bodies 27 in two rows, theconductive circuitry layer 5 of the light emitting device 1 constructs a7-series and 2-parallel circuit. The series connection equalizes theflowing current throughout the all light-emitting-diode main bodies 27.

The light transmissive insulator 13 is embedded between the lighttransmissive supportive substrate 2 and the light transmissivesupportive substrate 3.

For the light transmissive insulator 4 and the light transmissiveinsulator 6, in order to make the light transmissive supportivesubstrate 2 and the light transmissive supportive substrate 3 flexible,for example, a resin sheet material that has the insulation property,the light transmissive property and the flexibility is applied. Exampleresin materials are polyethylene terephthalate (PET), a polyethylenenaphthalate (PEN), polycarbonate (PC), polyethylene succinate (PES), acyclic olefin resin (e.g., ARTON (product name) available from JSRCorporation), and an acrylic resin.

It is preferable that the total light transmissivity of the lighttransmissive insulators 4, 6 should be equal to or higher than 90%, andmore preferably, equal to or higher than 95%. Note that the total lighttransmissivity is defined in, for example, JIS K7105.

It is preferable that the thickness of the light transmissive insulator4 and that of the light transmissive insulator 6 should be within arange between, for example, 50 to 300 μm. When the thickness of thelight transmissive insulator 4 and that of the light transmissiveinsulator 6 exceed 300 μm, it becomes difficult to give an excellentflexibility to the light transmissive supportive substrate 2 and to thelight transmissive supportive substrate 3, possibly decreasing the lighttransmissive property. Conversely, when the thickness of the lighttransmissive insulator 4 and that of the light transmissive insulator 6are less than 50 μm, at the time of vacuum thermal compression bonding,the light transmissive insulator 4 and the light transmissive insulator6 become out of shape around the light emitting diode 22, which is notsuitable.

The conductive circuitry layer 5 is formed of a transparent conductivematerial, such as indium tin oxide (ITO), fluorine-doped tin oxide(FTO), zinc oxide, or indium zinc oxide (IZO). The conductive circuitrylayer 5 can be formed by, for example, forming a thin film by sputteringor electron beam vapor deposition, and patterning the obtained thin filmby laser processing or etching, etc.

In addition, the conductive circuitry layer 5 may be formed by, forexample, applying a mixture of micro particle of the transparentconductive material that has an average grain size within a rangebetween 10 to 300 nm with a transparent resin binder in a circuit shapeby screen printing, etc., or by a patterning process performed on theapplied film of the above mixture by laser processing orphotolithography to form a circuit.

The conductive circuitry layer 5 is not limited to the transparentconductive material, but may be formed by applying micro particle of anon-transparent conductive material, such as gold or silver, in a meshshape. For example, after a photosensitive compound of a non-transparentconductive material like silver halide is applied, exposure anddevelopment processes are performed to form the conductive circuitrylayer 5 in a mesh shape. In addition, a slurry containing micro particleof the non-transparent conductive material may be applied in a meshshape by screen printing, etc., to form the conductive circuitry layer5.

It is sufficient if the conductive circuitry layer 5 shows the lighttransmissive property when formed on the surface of the lighttransmissive insulator 4 to obtain the light transmissive supportivesubstrate 2.

It is preferable that the conductive circuitry layer 5 should have thelight transmissive property in such a way that the total lighttransmissivity (JIS K7105) of the light transmissive supportivesubstrate 2 becomes equal to or higher than 10% and the total lighttransmissivity as a whole light emitting device 1 becomes equal to orhigher than 1%. When the total light transmissivity as a whole lightemitting device 1 is lower than 1%, a light emitting dot isunrecognizable as a bright point. It is preferable that, depending onthe structure of the conductive circuitry layer 5, the conductivecircuitry layer 5 itself should have the light transmissive propertywithin a range between 10 to 85%

The light transmissive insulator 13 is embedded in a space between thelight transmissive supportive substrate 2 and the light transmissivesupportive substrate 3, i.e., a space except a part where the pluralityof light emitting diodes 22 is laid out. It is preferable that the lighttransmissive insulator 13 should be formed of a material containingelastomer as a major element, and may contain other resin components asneeded. Example known elastomers are acrylic-based elastomer,olefin-based elastomer, styrene-based elastomer, ester-based elastomer,and urethane-based elastomer. Among those elastomers, the acrylic-basedelastomer that satisfies the above-explained characteristics is asuitable material for the light transmissive insulator 13 since suchelastomer has, in addition to the light transmissive property, theelectrical insulation property, and the flexibility, excellent fluiditywhen soften, adhesion property after cured, and weather resistance, etc.

It is preferable that the light transmissive insulator 13 should beformed of a light transmissive insulation resin, in particular,elastomer that satisfies predetermined characteristics, such as a Vicatsoftening temperature, a tensile storage elastic modulus, a glasstransition temperature, and a melting-point temperature. For example, itis preferable that with the Vicat softening temperature being within arange between 80 to 160° C., the tensile storage elastic modulus between0 to 100° C. should be within a range between 0.01 to 10 GPa. Inaddition, it is preferable that the light transmissive insulator 13should not be melted at the Vicat softening temperature, and have thetensile storage elastic modulus of equal to or higher than 0.1 Mpa atthe Vicat softening temperature.

It is preferable that the light transmissive insulator 13 should have amelting-point temperature of equal to or higher than 180° C. or amelting-point temperature higher than the Vicat softening temperature byequal to or higher than 40° C. In addition, it is preferable that thelight transmissive insulator 13 should have a glass transitiontemperature of equal to or lower than −20° C. Note that the Vicatsoftening temperature is a value obtained under the A 50 conditiondescribed in JIS K7206 (ISO 306: 2004) at the test load of 10 N and atemperature rise rate of 50° C./hour.

The glass transition temperature and the melting-point temperature arevalues obtained through a heat flux differential scanning calorimetry ata temperature rise rate of 5° C./min using a differential scanningcalorimeter in accordance with a scheme conforming to JIS K7121 (ISO3146). The tensile storage elastic modulus is a value obtained at afrequency of 10 Hz using a dynamic viscosity automated measuringinstrument by rising a temperature from −100° C. to 200° C. at atemperature rise equal rate of 1° C./min conforming to JIS K7244-1 (ISO6721).

The light transmissive insulator 13 can be disposed up to theperipheries of the electrodes 28, 29. That is, when the electrodes 28,29 each have a smaller area than that of the electrode formation surface(e.g., light emitting surface) of the light-emitting-diode main body 27,and are in a shape protruding from the electrode formation surface, withthe electrodes 28, 29 being in contact with the conductive circuitrylayer 5, a space is formed between a part (a part where no electrode 28,29 is formed) of the electrode formation surface where no electrode 28,29 is formed and the conductive circuitry layer 5. It is preferable tofill the light transmissive insulator 13 in such a tiny space betweenthe part where no electrode 28, 29 is formed and the conductivecircuitry layer 5.

The light transmissive insulator 13 has a thinner thickness than aheight Tl of the light emitting diode 22 in order to improve the contactcharacteristic between the conductive circuitry layer 5 and theelectrodes 28, 29. The light transmissive supportive substrate 2intimately in contact with the light transmissive insulator 13 is formedin a curved shape inwardly from a part where the light emitting diode 22is laid out and toward the middle portion between the adjoining lightemitting diodes 22. Hence, the light transmissive supportive substrate 2pushes the conductive circuitry layer 5 against the electrodes 28, 29.Accordingly, the electrical connection between the conductive circuitrylayer 5 and the electrodes 28, 29, and the reliability thereof can beimproved.

The electrode 29 provided on the light emitting surface of thelight-emitting-diode main body 27 has a smaller area than that of thelight emitting surface so as not to disturb light emission from theactive layer 25 to the external space. FIG. 3 illustrates an exampleconnection between the conductive circuitry layer 5 and the lightemitting diode 22 according to this embodiment. The light emitting diode22 is connected to the conductive circuitry layer 5. The conductivecircuitry layer 5 is formed of, for example, a light transmissiveconductive material, but as explained above, the material thereof is notlimited to this example. In addition, the pattern of the conductivecircuitry layer 5 is not limited to this example, and various changescan be made thereto.

According to this embodiment, in the flexible light transmissive lightemitting device that has embedded light emitting diodes, even if, forexample, the pad electrode is flexed in a concave shape, the conductivebump 30 ensures a sufficient height, and thus a short-circuit can beprevented.

[Manufacturing Method]

FIGS. 4A to 4D are diagrams for explaining a manufacturing method of thelight emitting device according to this embodiment. The manufacturingmethod of the light emitting device according to this embodiment will beexplained with reference to FIGS. 4A to 4D.

First, the light emitting diode 22 that has the electrode 28 and theelectrode 29 (anode electrode and cathode electrode or cathode electrodeand anode electrode) already formed is prepared.

Next, the conductive bumps 30 are respectively formed on the electrodes28, 29 of the light emitting diode 22. As for the method of forming theconductive bump 30, a method of forming a gold or gold alloy bump froman Au wire or an Au alloy wire using a wire bump forming machine isapplicable. It is preferable that the applied wire should have adiameter of equal to or larger than 15 μm and equal to or smaller than75 μm.

In this embodiment, a wire bonding apparatus is applied, discharging isperformed on the wire tip to melt the metal and to form a ball. Next,ultrasound is applied to connect such a ball to the pad electrode.Subsequently, with the ball being connected to the pad electrode, thewire is cut out from the ball.

[Rounding Process]

A tiny protruding burr left on the top of the ball may be left as it is,but a rounding process of depressing the upper surface of the ball toround the upper surface thereof may be performed when desirable. In thelatter case, a tamping process may be performed by a presser using aresin sheet, but the upper surface of the ball may be pressed by the tipof a jig of the wire bonding apparatus. When the depressing-typerounding process is performed, the curvature factor of the upper surfaceof the ball becomes slightly larger than that of the lower portion ofthe ball.

FIG. 5 is an exemplary diagram illustrating a shape of a bump (ball)before the rounding process. As illustrated in FIG. 5, the conductivebump 30 has a remaining wire cut out when the bump is formed. Thisremaining wire is called a tail. When the diameter of a surface incontact with the pad electrode of the LED is A and the height of thebump is B, it is desirable that the conducive bump 30 should have ashape which satisfies a condition B/A=0.2 to 0.7. Hence, as for the tailthat is out of this numerical range, the rounding process is performed.

FIGS. 6A to 6C are diagrams for explaining the rounding process using ajig. After a bump is formed, the light emitting diode is placed (seeFIG. 6A) on the stage of a bump bonding apparatus (unillustrated). A jigattached to the bump bonding apparatus and harder than the bump isdepressed against the upper portion of the bump with the lower surfaceof the jig being in parallel with the electrode (see FIG. 6B). At thistime, the jig is continuously depressed until the height of the bumpbecomes the desired height B. Consequently, the wire left at the upperportion when the wire is cut out at the time of bump formation iscrushed (see FIG. 6C), and thus a continuous surface that has noprotrusion is formed on the bump.

FIGS. 7A to 7C are diagrams for explaining the rounding process by apress work using a resin sheet. FIG. 8A is a diagram illustrating alayout of the light emitting diodes prior to a press work. FIG. 8B is adiagram for explaining the layout of the LED chips after the press work.A resin sheet 200 that is thicker than a height obtained by adding theheight B of the formed bump with the thickness of the LED chip is placedon the lower plate of a pressing apparatus, the LED chips formed withbumps are placed on the resin sheet 200, and a resin sheet 100 that isthicker than a height obtained by adding the height B of the formed bumpwith the thickness Of the LED chip is placed on the LED chips (see FIG.7A). In this case, example materials for the resin sheets 100, 200 aresuch as PET, a fluorine resin, TPX, and olefin.

As illustrated in FIG. 8A, when pressure is applied so as to hold thelight emitting diodes between the press upper plate of the pressingapparatus and the press lower plate thereof to perform pressing (seeFIG. 7B), as illustrated in FIG. 8B, the bump formation surface of thelight emitting diode is embedded in the resin sheet 100. In addition,the opposite surface of the LED chip to the bump formation surface isembedded in the resin sheet 200.

After the press work as illustrated in FIG. 8B, the resin sheets 100,200 are peeled off. Consequently, the wire portion of the bump formed onthe LED chip and left on the upper portion of the bump when the wire iscut at the time of bump formation has been crushed by the resin sheet100, and thus a continuous surface is formed on the upper portion of thebump (see FIG. 7C). At this time, by adjusting the resin hardness andthe pressing force, the bump height B can be adjusted. Note that the LEDchip may be directly disposed on the press lower plate without the resinsheet 200 being disposed at the time of pressing.

In the case of the press work scheme using the resin sheet, incomparison with the rounding method using the jig, the continuoussurface formed on the upper portion of the bump becomes a roundedsurface. Hence, although the conductive bump is formed on the padelectrode using a metal ball, in addition to the wire bump, electrolyticplating, non-electrolytic plating, inkjet application using an ink thatcontains metal micro particle, application or printing of a paste thatcontains metal micro particle, thermal compression bonding of a ballmounting and pellet mounting anisotropy conductive film, etc., enableapplication of metal, such as gold, silver, copper, or nickel, an alloylike a gold-tin alloy, eutectic, amorphous and a solder.

Next, the light transmissive supportive substrate 2 that includes thelight transmissive insulator 4 and the conductive circuitry layer 5formed on the surface of the light transmissive insulator 4, and, thelight transmissive supportive substrate 3 that includes the lighttransmissive insulator 6 only are prepared. The material of theconductive circuitry layer 5 and the formation method thereof, etc., areas explained above.

Next, the light transmissive insulation resin sheet 13′ that has a Vicatsoftening temperature within a range between 80 to 160° C. is prepared.In addition to the above-explained Vicat softening temperature, it ispreferable that the light transmissive insulation resin sheet 13′ shouldcontain a resin that is a major element which does not melt at the Vicalsoftening temperature with the tensile storage elastic modulus beingwithin a range between 0.01 and 10 GPa within a temperature rangebetween 0 to 100° C., has the tensile storage elastic modulus of equalto or higher than 0.1 MPa at the Vicat softening temperature, has themelting-point temperature of equal to or higher than 180° C. or higherthan the Vicat softening temperature by equal to or higher than 40° C.,and has the glass transition temperature of equal to or lower than −20°C. It is preferable that the light transmissive insulation resin sheet13′ should be formed of an elastomer sheet, and more preferably, anacrylic-based elastomer sheet.

Next, the light transmissive insulation resin sheet 13′ is disposed onthe conductive circuitry layer 5 of the light transmissive supportivesubstrate 2 so as to cover the entire conductive circuitry layer 5 (seeFIG. 4A). For example, the light transmissive insulation resin sheet 13′is tentatively attached by an adhesive.

The light transmissive insulation resin sheet 13′ is formed in a shapethat is capable of covering the whole conductive circuitry layer 5 andthe whole light transmissive insulator 4 including the portion where thelight emitting diode 22 is to be disposed on the conducive circuitrylayer 5. The plurality of light emitting diodes 22 is disposed on thelight transmissive insulation resin sheet 13′ (see FIG. 4B). The lightemitting diodes 22 are disposed in such a way that the electrodes 28, 29are located at the light-transmissive-insulation-resin-sheet-13′ side,i.e., at the conductive-circuitry-layer-5 side. The light transmissivesupportive substrate 3 is disposed on the light emitting diodes 22 (seeFIG. 4C).

By executing the processes illustrated in FIG. 4A to FIG. 4C, with theelectrodes 28, 29 being located at the conductive-circuitry-layer-5side, the light emitting diode 22 is laid out between the lighttransmissive supportive substrate 2 and the light transmissivesupportive substrate 3.

It is appropriate if the light transmissive insulation resin sheet 13′has a thickness capable of sufficiently filling a space between thelight transmissive supportive substrate 2 and the light transmissivesupportive substrate 3 in a vacuum thermal compression bonding processto be explained later, i.e., a space based on the gap between the lighttransmissive supportive substrate 2 and the light transmissivesupportive substrate 3 produced by the laid-out light emitting diodes22.

More specifically, it is appropriate if the thickness of the lighttransmissive insulation resin sheet 13′ is capable of sufficientlyfilling a gap between the light transmissive supportive substrate 2 andthe light transmissive supportive substrate 3 based on the height of thelight emitting diode 22. When a thickness (T) of the light transmissiveinsulator 13 is designed so as to be thinner than the height (H) of thelight emitting diode 22, it is appropriate to design the thickness ofthe light transmissive insulation resin sheet 13′ in accordance with adifference (H-T).

Next, as illustrated in FIG. 4D, a laminated body that includes thelight transmissive supportive substrate 2, the light transmissiveinsulation resin sheet 13′, the light emitting diodes 22, and the lighttransmissive supportive substrate 3 laminated in this order ispressurized under a vacuum condition while being heated.

As for the heating and pressurizing process (vacuum thermal compressionbonding process) for the laminated body under the vacuum condition, itis preferable that heating and pressurizing are performed on thelaminated body up to a temperature T within a range Mp−10 (° C.)≤T≤Mp+30(° C.) where Mp is the Vicat softening temperature (° C.) of the lighttransmissive insulation resin sheet 13′. A more preferable heatingtemperature is within a range Mp−10 (° C.)≤T≤Mp+10 (° C.).

By applying such a heating condition, it becomes possible to pressurizethe laminated body with the light transmissive insulation resin sheet13′ being softened appropriately. The electrodes 28, 29 disposed on theconductive circuitry layer 5 via the light transmissive insulation resinsheet 13′ are connected to the predetermined portions of the conductivecircuitry layer 5, and the softened light transmissive insulation resinsheet 13′ is embedded between the light transmissive supportivesubstrate 2 and the light transmissive supportive substrate 3, therebyforming the light transmissive insulator 13.

When a heating temperature T of the laminated body at the time of vacuumthermal compression bonding is lower than a temperature (T<Mp−10) thatis lower than the Vicat softening temperature Mp of the lighttransmissive insulation resin sheet 13′ by 10 (° C.), the softening ofthe light transmissive insulation resin sheet 13′ becomes insufficient,resulting in a possibility that the adhesion of the light transmissiveinsulation resin sheet 13′ (and thus light transmissive insulator 13) tothe light emitting diode 22 decreases. When the heating temperature T ofthe laminated body exceeds a temperature (Mp+30<T) that is higher thanthe Vicat softening temperature Mp of the light transmissive insulationresin sheet 13′ by 30 (° C.), the light transmissive insulation resinsheet 13′ becomes too soft, possibly causing a defective shape.

<Thermal Compression Bonding Process>

It is preferable that the thermal compression bonding process for thelaminated body in the vacuum condition should be carried out as follow.The above-explained laminated body is pre-pressurized to causerespective components intimately in contact with each other. Next, airin a work space where the pre-pressurized laminated body is disposed isdrawn to accomplish the vacuum condition, and pressurization isperformed while the laminated body is heated to the above-explainedtemperature. By performing thermal compression bonding on thepre-pressurized laminated body under the vacuum condition in this way,the softened light transmissive insulation resin sheet 13′ can be filledin the space between the light transmissive supportive substrate 2 andthe light transmissive supportive substrate 3 without any void.

It is preferable that the vacuum condition at the time of thermalcompression bonding should be equal to or lower than 5 kPa. Thepre-pressurizing process may be omitted, but in this case, misalignment,etc., is likely to occur in the laminated body, and thus execution ofthe pre-pressurizing process is preferable.

When the thermal compression bonding process for the laminated body isperformed under an atmospheric condition or a low vacuum condition, airbubbles are likely to be left in the light emitting device 1 havingundergone the thermal compression bonding, in particular, around thelight emitting diode 22. Since the air bubbles left in the lightemitting device 1 are pressurized, this may cause an expansion of thelight emitting device 1 having undergone the thermal compression bondingor a peeling of the light emitting diode 22 from the light transmissivesupportive substrate 2 and the light transmissive supportive substrate3. In addition, when the air bubbles and expansion are present in thelight emitting device 1, in particular, near the light emitting diode22, light will be scattered non-uniformly, which is not preferable sinceit becomes a problem in the visual inspection of the light emittingdevice 1.

With the light transmissive insulation resin sheet 13′ being presentbetween the conductive circuitry layer 5 and the electrodes 28, 29 ofthe light emitting diode 22, by performing the vacuum thermalcompression bonding, the electrodes 28, 29 can be electrically connectedto the conductive circuitry layer 5, while at the same time, the lighttransmissive insulator 13 intimately in contact with the periphery ofthe light emitting diode 22 can be formed. In addition, a part of thelight transmissive insulator 13 can be filled excellently in the spacebetween the part of the light emitting surface of thelight-emitting-diode main body 27 where no electrode 28, 29 is formedand the conductive circuitry layer 5.

According to the manufacturing method in this embodiment, the lightemitting device 1 which has the improved electrical connection betweenthe conductive circuitry layer 5 and the electrodes 28, 29 of the lightemitting diode 22 and the enhanced reliability thereof can bemanufactured with an excellent reproducibility.

FIG. 13 is a diagram illustrating the light emitting diode 22constructing the light emitting device 1, and the light transmissiveinsulator 13, the conductive circuitry layer 5, and, the lighttransmissive insulators 4, 6 located around the light emitting diode 22.In addition, FIG. 14 is a diagram illustrating the conductive bumps 30formed on the electrodes 28, 29 of the light emitting diode 22 in anenlarged manner. As is clear from FIGS. 13 and 14, according to thelight emitting device 1, the conductive circuitry layer 5 has a contactarea with the conductive bump 30 of the light emitting diode 22 concavedalong the conductive bump 30. Hence, the contact area between theconductive bump 30 and the conductive circuitry layer 5 can beincreased. Consequently, a resistance between the conductive bump 30 andthe conductive circuitry layer 5 can be reduced.

In this embodiment, although the explanation has been given of anexample case in which the light transmissive insulator 13 is formed of asingle-layer sheet, the light transmissive insulator 13 may be formed oftwo light transmissive insulation resin sheets, and with the lightemitting diode being held between the two light transmissive insulationresin sheets, pressurization may be applied to the light transmissivesupportive substrate 2 and the light transmissive supportive substrate 3to obtain the structure illustrated in FIG. 2.

In addition, at this time, the light transmissive supportive substrate 3may be utilized as a tentative base, and the whole structure may bepressurized to accomplish an electrical connection between theelectrodes 28, 29 and the conductive circuitry layer 5. Subsequently,either one of the two light transmissive resin sheets at the oppositeside to the electrodes 28, 29 may be peeled, and the light transmissiveresin sheet that has the same thickness as that of the peeled sheet andthe eventual light transmissive supportive substrate 3 may be laid overto accomplish the structure illustrated in FIG. 2.

[Second Embodiment]

Next, an explanation will be given of a light emitting device accordingto a second embodiment of the present disclosure with reference to theaccompanying figures. Note that as for the similar structure to that ofthe light emitting device in the first embodiment, the explanationthereof will be omitted below.

FIG. 9 is an exemplary sectional diagram illustrating a schematicstructure of a light emitting device 1 according to this embodiment. Inaddition, FIG. 10 is a cross-sectional view illustrating a part of thelight emitting device 1 in FIG. 9 in an enlarged manner. The lightemitting device of this embodiment differs from the light emittingdevice of the first embodiment that the light emitting diodeconstructing the light emitting device has electrodes on both surfaces.

As illustrated in FIG. 9, the light emitting device 1 roughly includesthe light transmissive supportive substrate 2, the light transmissivesupportive substrate 3, a light emitting diode 8, and the lighttransmissive insulator 13.

The light transmissive supportive substrate 2 includes the lighttransmissive insulator 4, and the conductive circuitry layer 5 formed ona surface of the light transmissive insulator 4. The light transmissivesupportive substrate 3 includes the light transmissive insulator 6, anda conductive circuitry layer 7 formed on a surface of the lighttransmissive insulator 6.

The light transmissive supportive substrate 2 and the light transmissivesupportive substrate 3 are disposed so as to cause the conductivecircuitry layer 5 and the conductive circuitry layer 7 to face with eachother with a predetermined gap therebetween. The light transmissiveinsulator 13 is present at portions except the light emitting diode 8between the light transmissive insulator 4 and the light transmissiveinsulator 6, the conductive circuitry layer 5, and the conductivecircuitry layer 7.

The single or the plurality of light emitting diodes 8 are laid outbetween the surface of the light transmissive supportive substrate 2 onwhich the conductive circuitry layer 5 is formed and the surface of thelight transmissive supportive substrate 3 on which the conductivecircuitry layer 7 is formed. The light emitting diode 8 has an electrode9 and an electrode 10 provided at the light-emitting-surface side andthe opposite-surface side, respectively. The electrode 9 is electricallyconnected to the conductive circuitry layer 5, while the electrode 10 iselectrically connected to the conductive circuitry layer 7,respectively.

A light emitting diode chip (LED chip) that contains a P-N junction canbe used as the light emitting diode 8. Note that the light emittingdiode 8 is not limited to the LED chip, and may be a laser diode (LD)chip, etc. As for the light emitting diode 8, for example, any of thefollowing structures is applicable: a structure having a P-typesemiconductor layer formed on an N-type semiconductor substrate; astructure having an N-type semiconductor layer formed on a P-typesemiconductor substrate; a structure having an N-type semiconductorlayer and a P-type semiconductor layer both formed on a semiconductorsubstrate; a structure having a P-type hetero semiconductor layer and anN-type hetero semiconductor layer both formed on a P-type semiconductorsubstrate; and a structure having an N-type hetero semiconductor layerand a P-type hetero semiconductor layer both formed on an N-typesemiconductor substrate. In addition, an LED that is a type having theLED bonded on a metal supportive substrate like CuW, or a semiconductorsupportive substrate, such as Si, Ge, GaAs, and the P-N junctiontransferred from the original semiconductor substrate to the supportivesubstrate is also applicable.

As illustrated in FIG. 10, the light emitting diode 8 applied in thisembodiment includes a light-emitting-diode main body 12 that includes alight emitting layer (light emitting part of P-N junction boundary or adouble hetero junction structure) 11 held between a P-type semiconductorlayer 16 or 17 and an N-type semiconductor layer 17 or 16, and theelectrodes 9 and 10 provided on the upper surface of thelight-emitting-diode main body 12 and the lower surface thereof,respectively.

As illustrated in FIG. 10, the electrode 9 contacts the conductivecircuitry layer 5 via a conductive bump 20, thereby being electricallyconnected to the conductive circuitry layer 5. The electrode 10 contactsthe conductive circuitry layer 7, thereby being electrically connectedto the conductive circuitry layer 7.

The light emitting diode 8 emits light by a DC voltage applied via theelectrodes 9, 10. In addition, the light-emitting-diode main body 12 mayalso contain a light reflection layer, a current diffusion layer, and alight transmissive electrode, etc. in this case, thelight-emitting-diode main body 12 also contains a light reflectionlayer, a current diffusion layer, and a light transmissive electrode.

The conductive bump 20 employs the same structure as that of theconductive bump in the first embodiment. It is preferable that theheight of the conductive bump 20 should be equal to or higher than 5 μmand equal to or lower than 50 μm, and more preferably, equal to orhigher than 10 μm and equal to or lower than 30 μm. When the height ofthe conductive bump 20 is less than 5 μm, the short-circuit preventioneffect between the conductive circuitry layer 5 and the semiconductorlayer 16 decreases, which is not suitable. Conversely, when the heightof the conductive bump 20 exceeds 50 μm, in the vacuum thermal pressingprocess in the manufacturing process of the light emitting device, theconductive bump 20 deforms the first support base, resulting in a poorvisual inspection result and a poor connection, which is not suitable.

In addition, as will be explained later in detail with reference to thefollowing example and table 1, it is preferable that a ratio a/b betweena vertical distance a from the surface of the LED chip to the tip of thebump and a maximum distance b between the bump center position in aplanar direction and the end of the LED chip should be equal to orlarger than 0.120 and equal to or smaller than 0.400 in order to ensurethe reliability of the light emitting device of the present disclosure,and more preferably, the ratio a/b should be equal to or larger than0.130 and equal to or smaller than 0.380.

It is preferable that a contact area between the electrode 9 of the LEDchip and the conductive bump 20 should be equal to or larger than 100μm² and equal to or smaller than 15000 μm², and more preferably, equalto or larger than 400 μm² and equal to or smaller than 8000 μm². Each ofthose dimensions are measured values under a stable environment in whicha room temperature and the temperature of a measurement object are 20°C.±2° C.

The conductive circuitry layer 5 and the conductive circuitry layer 7are formed on the respective surfaces of the light transmissiveinsulators 4, 6. The conductive circuitry layer 7 employs the similarstructure to that of the conductive circuitry layer 5 explained in thefirst embodiment.

The light transmissive insulator 13 is embedded in a space between thelight transmissive supportive substrate 2 and the light transmissivesupportive substrate 3 except a part where the plurality of lightemitting diodes 8 is disposed. It is preferable that the lighttransmissive insulator 13 should not be melted at the Vicat softeningtemperature and have the tensile storage elastic modulus of equal to orhigher than 0.1 MPa at the Vicat softening temperature. It is preferablethat the light transmissive insulator 13 should have a melting-pointtemperature of equal to or higher than 180° C. or a melting-pointtemperature higher than the Vicat softening temperature by equal to orhigher than 40° C. In addition, it is preferable that the lighttransmissive insulator 13 should have a glass transition temperature ofequal to or lower than −20° C.

It is further preferable that the elastomer which is the material forthe light transmissive insulator 13 should have a peel strength (throughmethod A defined in JIS C5061 8.1.6) of equal to or higher than 0.49N/mm for the light transmissive insulator 13 formed of that materialrelative to the conductive circuitry layers 5, 7.

By applying the elastomer, etc., that satisfies the above-explainedVicat softening temperature, tensile storage elastic modulus, andmelting-point temperature, with the light transmissive insulator 13being intimately in contact with the plurality of light emitting diodes8, the light transmissive insulator 13 can be embedded between the lighttransmissive supportive substrate 2 and the light transmissivesupportive substrate 3. In other words, the contacting condition betweenthe conductive circuitry layer 5 and the electrode 9 (a first electrodewith a bump, the same is true in the following explanation), and thecontacting condition between the conductive circuitry layer 7 and theelectrode 10 are maintained by the light transmissive insulator 13 thatis disposed so as to be intimately in contact with the periphery of thelight emitting diode 8.

Hence, the electrical connection reliability between the conductivecircuitry layer 5 and the electrode 9, and that between the conductivecircuitry layer 7 and the electrode 10 can be enhanced when, inparticular, a flex test, a thermal cycle test (TCT), etc., are performedon the light emitting device 1.

When the Vicat softening temperature of the light transmissive insulator13 exceeds 160° C., the light transmissive insulation resin sheet doesnot sufficiently deform in a process of forming the light transmissiveinsulator 13 to be explained later, and thus the electrical connectionbetween the conductive circuitry layer 5 and the electrode 9, and thatbetween the conductive circuitry layer 7 and the electrode 10 decrease.When the Vicat softening temperature of the light transmissive insulator13 is lower than 80° C., the holding of the light emitting diode 8decreases, and thus the electrical connection reliability between theconductive circuitry layer 5 and the electrode 9, and that between theconductive circuitry layer 7 and the electrode 10 decrease. It ispreferable that the Vicat softening temperature of the lighttransmissive insulator 13 should be equal to or higher than 100° C. Thisfurther enhances the electrical connection reliability between theconductive circuitry layer 5 and the electrode 9, and that between theconductive circuitry layer 7 and the electrode 10. It is preferable thatthe Vicat softening temperature of the light transmissive insulator 13should be equal to or lower than 140° C. This further enhances theelectrical connection between the conductive circuitry layer 5 and theelectrode 9, and that between the conductive circuitry layer 7 and theelectrode 10.

When the tensile storage elastic modulus of the light transmissiveinsulator 13 between 0 and 100° C. is less than 0.01 GPa, the electricalconnection between the conductive circuitry layer 5 and the electrode 9,and that between the conductive circuitry layer 7 and the electrode 10also decrease.

Since the light emitting diode 8, and the electrodes 9, 10 thereof aremicrostructures, in order to precisely connect the electrodes 9, 10 ofthe plurality of light emitting diodes 8 at the time of vacuum thermalcompression bonding to be explained later to the predetermined portionsof the conductive circuitry layer 5 and conductive circuitry layer 7, itis necessary for the light transmissive insulation resin sheet 13′ tomaintain a relatively high storage elastic modulus from the roomtemperature to the temperature around the heating temperature of thevacuum thermal compression bonding process.

When the elastic modulus of the resin decreases at the time of vacuumthermal compression bonding, a tilting of the light emitting diode 8 anda lateral fine displacement thereof occur during the process, resultingin an unsuccessful electrical connection between the electrode 9, 10 andthe conductive circuitry layer 5, 7, or an increase in the connectionresistance, etc. Those are factors that will decrease the manufacturingyield of the light emitting device 1 and the reliability thereof. Inorder to avoid those events, the light transmissive insulator 13 thathas a tensile storage elastic modulus of equal to or higher than 0.01GPa between 0 to 100° C. is applied.

When, however, the storage elastic modulus is too high, the flexresistance, etc., of the light emitting device 1 decreases, and thus thelight transmissive insulator 13 that has a tensile storage elasticmodulus of equal to or lower than 10 GPa between 0 to 100° C. isapplied. It is preferable that the light transmissive insulator 13should have a tensile storage elastic modulus of equal to or higher than0.1 GPa between 0 to 100° C., and equal to or lower than 7 GPa.

When the elastomer, etc., that forms the light transmissive insulator 13is not melted at the Vicat softening temperature, and the tensilestorage elastic modulus at the Vicat softening temperature is equal toor higher than 0.1 MPa, the vertical positional precision among theelectrodes 9, 10 and the conductive circuitry layers 5, 7 at the time ofvacuum thermal compression bonding can be further improved.

In view of the foregoing, it is preferable that the elastomer formingthe light transmissive insulator 13 should have a melting-pointtemperature of equal to or higher than 180° C. or a melting-pointtemperature higher than the Vicat softening temperature by equal to orhigher than 40° C. It is more preferable that the tensile storageelastic modulus of the elastomer at the Vicat softening temperatureshould be equal to or higher than 1 MPa. In addition, it is morepreferable that the melting-point temperature of the elastomer should beequal to or higher than 200° C. or a melting-point temperature higherthan the Vicat softening temperature by equal to or higher than 60° C.

Still further, in order to improve not only the manufacturability of thelight emitting device 1 but also the flex resistance of the lightemitting device 1 and the thermal cycle resistance characteristicthereof across a broad temperature range from a low temperature to ahigh temperature, it is important for the light transmissive insulator13 to have a balance among characteristics that are the Vicat softeningtemperature, the tensile storage elastic modulus, and the glasstransition temperature. By applying the elastomer that satisfies theabove-explained tensile storage elastic modulus, the flex resistance ofthe light emitting device 1 and the thermal cycle resistancecharacteristic thereof can be enhanced.

However, depending on an outdoor application and a living environment inwinter although in an indoor application, a flex resistance and athermal cycle resistance characteristic at a low temperature arerequired. When the glass transition temperature of the elastomer is toohigh, the flex resistance of the light emitting device 1 and the thermalcycle resistance characteristic thereof under a low-temperatureenvironment may decrease. Hence, it is preferable to apply the elastomerthat has a glass transition temperature of equal to or lower than −20°C. Based on such glass transition temperature and tensile storageelastic modulus, the flex resistance of the light emitting device 1 andthe thermal cycle resistance characteristic thereof can be improvedacross a broad temperature range from a low temperature to a hightemperature. It is more preferable that the glass transition temperatureof the elastomer should be equal to or lower than −40° C.

The thickness of the light transmissive insulator 13 may be equal to agap between the light transmissive supportive substrate 2 and the lighttransmissive supportive substrate 3 based on the height of the lightemitting diode 8, but in order to enhance the contact between theconductive circuitry layer 5, 7 and the electrode 9, 10, such athickness should be preferably thinner than the height of the lightemitting diode 8. In addition, it is more preferable to design that athickness (T) of the light transmissive insulator 13 should satisfy acondition such that a difference (H−T) from a height (H) of the lightemitting diode 8 is within a range between 5 to 200 μm.

However, when the thickness (T) of the light transmissive insulator 13is too thin, it may become difficult to maintain the shape of the lighttransmissive insulator 13 and the intimate adhesion, etc., relative tothe light emitting diode 8 may decrease. Hence, it is preferable thatthe difference (H−T) between the height (H) of the light emitting diode8 and the thickness (T) of the light transmissive insulator 13 should beequal to or smaller than ½ of the height (H) of the light emitting diode8.

According to this embodiment, in the flexible light transmissive lightemitting device that has the light emitting diodes embedded therein,even if such a device is flexed, the conductive bump 20 ensures thesufficient height, and thus a short-circuit can be prevented.

<Manufacturing Method>

FIGS. 11A to 11D are diagrams for explaining the manufacturing method ofthe light emitting device according to this embodiment. Themanufacturing method of the light emitting device 1 according to thisembodiment will be explained with reference to FIGS. 11A to 11D.

First of all, the light emitting diode 8 that has the electrode 9 formedon one side and the electrode 10 formed on the other side (anodeelectrode and cathode electrode or cathode electrode and anodeelectrode) is prepared. Next, the conductive bump 20 is formed on theelectrode 9 (electrode pad) of the LED chip. As for the method offorming the conductive bump 20, a method of forming a gold or gold alloybump from an Au wire or an Au alloy wire using a wire bump formingmachine is applicable. It is preferable that the applied wire shouldhave a diameter of equal to or larger than 15 μm and equal to or smallerthan 75 μm.

In this embodiment, a wire bonding apparatus is applied, discharging isperformed on the wire tip to melt the metal and to form a ball. Next,ultrasound is applied to connect such a ball to the pad electrode.Subsequently, with the ball being connected to the pad electrode, thewire is cut out from the ball. As for the bump 20, like the bump 30 inthe first embodiment, the rounding process is performed. In this case,this rounding process may be performed using a resin sheet.

FIG. 12A is a diagram illustrating a layout of the light emitting diodesprior to a press work. FIG. 12B is a diagram illustrating the layout ofthe light emitting diodes after the press work. As illustrated in FIG.12A, when pressure is applied so as to hold the light emitting diodesbetween the press upper plate of the press apparatus and the press lowerplate thereof to perform pressing, as illustrated in FIG. 12B, the bumpformation surface of the light emitting diode is embedded in the resinsheet 100. In addition, the opposite surface of the light emitting diodeto the bump formation surface is embedded in the resin sheet 200.

After the presswork as illustrated in FIG. 12B, the resin sheets 100,200 are peeled off. Consequently, the wire portion of the bump formed onthe LED chip and left on the upper portion of the bump when the wire iscut at the time of bump formation has been crushed by the resin sheet100, and thus a continuous surface is formed on the upper portion of thebump (see FIG. 7C). At this time, by adjusting the resin hardness andthe pressing force, the bump height B can be adjusted. Note that the LEDchip may be directly disposed on the press lower plate without the resinsheet 200 being disposed at the time of pressing.

Next, the light transmissive supportive substrate 2 that includes thelight transmissive insulator 4 and the conductive circuitry layer 5formed on the surface thereof, and, the light transmissive supportivesubstrate 3 that includes the light transmissive insulator 6 and theconductive circuitry layer 7 formed on the surface thereof, areprepared. The material and formation method of the conductive circuitrylayer 5 and those of the conductive circuitry layer 7 are the same asthose explained above.

Next, the light transmissive insulation resin sheet 14 that has a Vicatsoftening temperature within a range between 80 to 160° C. is prepared.In addition to the above-explained Vicat softening temperature, it ispreferable that the light transmissive insulation resin sheet 14 shouldcontain a resin that is a major element which does not melt at the Vicalsoftening temperature with the tensile storage elastic modulus beingwithin a range between 0.01 and 10 GPa within a temperature rangebetween 0 to 100° C., has the tensile storage elastic modulus of equalto or higher than 0.1 MPa at the Vicat softening temperature, has themelting-point temperature of equal to or higher than 180° C. or higherthan the Vicat softening temperature by equal to or higher than 40° C.,and has the glass transition temperature of equal to or lower than −20°C. It is preferable that the light transmissive insulation resin sheet14 should be formed of an elastomer sheet, and more preferably, anacrylic-based elastomer sheet.

Next, the light transmissive insulation resin sheet 14 is disposed onthe conductive circuitry layer 5 of the light transmissive supportivesubstrate 2 so as to cover the entire conductive circuitry layer 5 (seeFIG. 11A). The light transmissive insulation resin sheet 14 is formed ina shape that is capable of covering the entire conductive circuitrylayer 5, in addition, the entire light transmissive insulator 4including a part of the conductive circuitry layer 5 where the lightemitting diode 8 is to be disposed.

Next, the plurality of light emitting diodes 8 is laid out on the lighttransmissive insulation resin sheet 14 (see FIG. 11B). The lightemitting diodes 8 are laid out in such a way that the electrode 9 onwhich the conductive bump 20 is formed is located at thelight-transmissive-insulation-resin-sheet-14 side, i.e., at theconductive-circuitry-layer-5 side.

The light transmissive supportive substrate 3 that has the conductivecircuitry layer 7 formed on the surface of the light transmissiveinsulator is disposed on the light emitting diodes 8 (see FIG. 11C).

By executing the processes illustrated in FIG. 11A to FIG. 11C, with theelectrode 9 being located at thelight-transmissive-insulation-resin-sheet-14 side, and the electrode 10being located at the light-transmissive-supportive-substrate-3 side, thelight emitting diode 8 is laid out between the light transmissiveinsulation resin sheet 14 and the light transmissive supportivesubstrate 3.

It is appropriate if the light transmissive insulation resin sheet 14has a thickness capable of sufficiently filling a space between thelight transmissive supportive substrate 2 and the light transmissivesupportive substrate 3 in a vacuum thermal compression bonding processto be explained later, i.e., a space based on the gap between the lighttransmissive supportive substrate 2 and the light transmissivesupportive substrate 3 produced by the laid-out light emitting diodes 8.

More specifically, it is appropriate if the thickness of the lighttransmissive insulation resin sheet 14 is capable of sufficientlyfilling a gap between the light transmissive supportive substrate 2 andthe light transmissive supportive substrate 3 based on the height of thelight emitting diode 8 as explained above. When the thickness (T) of thelight transmissive insulator 13 is designed so as to be thinner than theheight (H) of the light emitting diode 8, it is appropriate to designthe thickness of the light transmissive insulation resin sheet 14 inaccordance with the difference (H−T).

Next, as illustrated in FIG. 11D, a laminated body that includes thelight transmissive supportive substrate 2, the light transmissiveinsulation resin sheet 14, the light emitting diodes 8, and the lighttransmissive supportive substrate 2 laminated in this order ispressurized under a vacuum condition while being heated.

As for the heating and pressurizing process (vacuum thermal compressionbonding process) for the laminated body under the vacuum condition, itis preferable that heating and pressurization are performed on thelaminated body up to a temperature T within a range Mp−10 (° C.)≤T≤Mp+30(° C.) where Mp is the Vicat softening temperature (° C.) of the lighttransmissive insulation resin sheet 14. A more preferable heatingtemperature is within a range Mp−10 (° C.)≤T≤Mp+10 (° C.). By applyingsuch a heating condition, with the light transmissive insulation resinsheet 14 being softened appropriately, the laminated body can bepressurized.

Hence, the electrode 9 with the bump disposed on the conductivecircuitry layer 5 via the light transmissive insulation resin sheet 14is connected to the predetermined portion of the conductive circuitrylayer 5, and the electrode 10 is connected to the predetermined portionof the conductive circuitry layer 7, and, the softened lighttransmissive insulation resin sheet 14 is embedded between the lighttransmissive supportive substrate 2 and the light transmissivesupportive substrate 3, thereby forming the light transmissive insulator13.

When a heating temperature T of the laminated body at the time of vacuumthermal compression bonding is lower than a temperature (T<Mp−10) thatis lower than the Vicat softening temperature Mp of the lighttransmissive insulation resin sheet 14 by 10 (° C.), the softening ofthe light transmissive insulation resin sheet 14 becomes insufficient,resulting in a possibility that the intimate adhesion of the lighttransmissive insulation resin sheet 14 (and thus light transmissiveinsulator 13) to the light emitting diode 8 decreases.

In addition, there is also a possibility that a part of the lighttransmissive insulation resin sheet 14 (and thus light transmissiveinsulator 13) is not properly filled in the space between the portion ofthe light emitting surface of the light-emitting-diode main body 12where no electrode 9 is formed and the conductive circuitry layer 5.When the heating temperature T exceeds a temperature (Mp+30<T) that ishigher than the Vicat softening temperature Mp of the light transmissiveinsulation resin sheet 14 by 30 (° C.), the light transmissiveinsulation resin sheet 14 becomes too soft, possibly causing a defectiveshape.

The connection between the electrode 10 and the conductive circuitrylayer 7 may be accomplished by a direct contact or via a conductiveadhesive, etc.

<Thermal Compression Bonding Process>

It is preferable that the thermal compression bonding process for thelaminated body in the vacuum condition should be carried out as follow.The above-explained laminated body is pre-pressurized to causerespective components intimately in contact with each other. Next, airin a work space where the pre-pressurized laminated body is disposed isdrawn to accomplish the vacuum condition, and pressurization isperformed while the laminated body is heated to the above-explainedtemperature. By performing thermal compression bonding on thepre-pressurized laminated body under the vacuum condition in this way,the softened light transmissive insulation resin sheet 14 can be filledin the space between the light transmissive supportive substrate 2 andthe light transmissive supportive substrate 3 without any void.

It is preferable that the vacuum condition at the time of thermalcompression bonding should be equal to or lower than 5 kPa. Thepre-pressurizing process may be omitted, but in this case, misalignment,etc., is likely to occur in the laminated body, and thus execution ofthe pre-pressurizing process is preferable.

When the thermal compression bonding process for the laminated body isperformed under an atmospheric condition or a low vacuum condition, airbubbles are likely to be left in the light emitting device 1 havingundergone the thermal compression bonding, in particular, around thelight emitting diode 8. Since the air bubbles left in the light emittingdevice 1 are pressurized, this may cause an expansion of the lightemitting device 1 having undergone the thermal compression bonding or apeeling of the light emitting diode 8 from the light transmissivesupportive substrate 2 and the light transmissive supportive substrate3. In addition, when the air bubbles and expansion are present in thelight emitting device 1, in particular, near the light emitting diode 8,light to be emitted will be scattered non-uniformly, which is notpreferable since it becomes a problem in the visual inspection of thelight emitting device 1.

In this embodiment, a production of air bubbles in the light emittingdevice 1 can be suppressed based on various characteristics of the lighttransmissive insulator 13 and the vacuum thermal compression bondingcondition, etc. It is preferable that there should be no remaining airbubble in the light emitting device 1 which has an outer diameter ofequal to or larger than 500 μm or is equal to or larger than theexternal dimension of the light emitting diode 8.

The pressurization force applied to the laminated body at the time ofvacuum thermal compression bonding varies depending on the heatingtemperature, the material and thickness of the light transmissiveinsulation resin sheet 14, and the final thickness of the lighttransmissive insulator 13, etc., but it is preferable that suchpressurization force should be normally within a range between 0.5 to 20MPa, and more preferably, within a range between 1 to 12 MPa. Byapplying such pressurization force, the performance of embedding thesoftened light transmissive insulation resin sheet 14 in the gap betweenthe light transmissive supportive substrate 2 and the light transmissivesupportive substrate 3 can be improved. In addition, a reduction of thecharacteristics of the light emitting diode 8 and a damage thereto,etc., can be suppressed.

As explained above, with the light transmissive insulation resin sheet14 being present between the conductive circuitry layer 5 and theelectrode 9 of the light emitting diode 8, by performing the vacuumthermal compression bonding process, the light transmissive insulator 13intimately in contact around the light emitting diode 8 can be obtainedwhile the electrode 9 with the bump and the electrode 10 areelectrically connected to the conductive circuitry layer 5 and theconductive circuitry layer 7, respectively. In addition, a part of thelight transmissive insulator 13 can be filled excellently in the spacebetween the portion of the light-emitting-diode main body 12 where noelectrode 9 is formed and the conductive circuitry layer 5, and thusremaining air bubbles can be suppressed. Hence, it becomes possible toobtain the light emitting device 1 that has enhanced electricalconnection reliability between the conductive circuitry layer 5, 7 andthe electrode 9, 10.

According to the manufacturing method in this embodiment, the lightemitting device which has the improved electrical connection between theconductive circuitry layers 5, 7 and the electrodes 9, 10 of the lightemitting diode 8 and the enhanced reliability thereof can bemanufactured with an excellent reproducibility.

As is clear from FIGS. 13 and 14, according to the light emitting device1, the conductive circuitry layer 5 has a contact area with theconductive bump 20 of the light emitting diode 8 concaved along theconductive bump 20. Hence, the contact area between the conductive bump20 and the conductive circuitry layer 5 can be increased. Consequently,a resistance between the conductive bump 20 and the conductive circuitrylayer 5 can be reduced.

In this embodiment, although the explanation has been given of anexample case in which the light transmissive insulator is formed of asingle-layer sheet, the light transmissive insulator may be formed oftwo light transmissive insulation resin sheets, and with the lightemitting diode being held between the two light transmissive insulationresin sheets, pressurization may be applied to the first lighttransmissive support base and the second light transmissive support baseto obtain the structure illustrated in FIG. 10.

EXAMPLE

Next, specific examples and evaluation results thereof will beexplained.

TABLE 1 DISTANCE DISTANCE FROM CHIP BETWEEN CHIP SURFACE ENDS MOST FLEXTEST TO DISTANCE FROM NUMBER NUMBER CHIP BUMP BUMP TIP POSITION BUMPCENTER FLEX OF LIGHT FLEX OF LIGHT SIZE HEIGHT (a) OF CHIPAND (b) RADIUSEMITTING RADIUS EMITTING μm□ μm μm BUMP μm a/b (mm) SAMPLES (mm) SAMPLESEXAMPLE 1 220 5 7 CHIP CENTER 156 0.045 50 3/6 40 0/6 EXAMPLE 2 350 5 7CHIP CENTER 247 0.028 50 2/6 40 0/6 EXAMPLE 3 220 10 12 CHIP CENTER 1560.077 50 4/6 40 0/6 EXAMPLE 4 350 10 12 CHIP CENTER 247 0.048 50 3/6 400/6 EXAMPLE 5 220 20 22 CHIP CENTER 156 0.141 50 6/6 20 6/6 EXAMPLE 6220 20 22 POSITION ¾ 233 0.094 50 5/6 30 1/6 FROM END OF CHIP ONDIAGONAL LINE EXAMPLE 7 350 20 22 CHIP CENTER 247 0.089 50 4/6 30 0/6EXAMPLE 8 220 30 32 CHIP CENTER 156 0.206 50 6/6 20 6/6 EXAMPLE 9 350 3032 CHIP CENTER 247 0.129 50 6/6 20 6/6 EXAMPLE 10 220 40 42 CHIP CENTER156 0.270 50 6/6 20 6/6 EXAMPLE 11 350 40 42 CHIP CENTER 247 0.170 506/6 20 6/6 EXAMPLE 12 220 50 52 CHIP CENTER 156 0.334 50 6/6 20 6/6EXAMPLE 13 350 50 52 CHIP CENTER 247 0.210 50 6/6 20 6/6 EXAMPLE 14 22060 65 CHIP CENTER 156 0.417 50 3/6 20 4/6 COMP 220 none — — — — 50 1/640 0/6 EXAMPLE 1 COMP 350 none — — — — 50 0/6 40 0/6 EXAMPLE 2

LED chips according to first to fourteenth examples in table 1 and tofirst to second comparative examples were prepared. All chips had athickness of 150 μm. A bump was formed on the first electrode of the LEDchip (in Examples 1-14) by a gold wire bonder, and the rounding processwas performed to produce a bump with a height indicated in table 1.

Next, polyethylene-terephthalate sheets that were first and second lighttransmissive supportive substrates with no bump and with a thickness of180 μm were also prepared. A silver mesh electrode was formed on thesurface of such a substrate to create a conductive circuitry layer.

A light transmissive insulation resin sheet that was an acrylic-basedelastomer sheet which had a Vicat softening temperature of 110° C., amelting-point temperature of 220° C., a glass transition temperature of−40° C., a tensile storage elastic modulus of 1.1 GPa at 0° C., thetensile storage elastic modulus of 0.3 GPa at 100° C., and the tensilestorage elastic modulus of 0.2 GPa at 110° C. that was the Vicatsoftening temperature, and, a thickness of 60 μm was prepared as thefirst and second light transmissive insulation resin sheets.

The Vicat softening temperature was obtained, using No. 148-HD-PC heatdistortion tester available from Yasuda Seiki Seisakusho Ltd., under acondition in which a test load was 10 N, and a temperature rise rate of50° C./hour, and also under A50 condition defined in JIS K7206 (ISO306).

The glass transition temperature and the melting-point temperature wereobtained by a method conforming to JIS K7121 (ISO 3146) using a DSC-60differential scanning calorimeter made by SHIMADZU Corporation through aheat flux differential scanning calorimetry at a temperature rise rateof 5° C./min.

The tensile storage elastic modulus was obtained, using a DDV-01 GPdynamic viscosity automated measuring instrument available from A & DCompany, Ltd., by rising a temperature from −100° C. to 200° C. at atemperature rise equal rate of 1° C./min conforming to JIS K7244-1 (ISO6721) and at a frequency of 10 Hz.

The second light transmissive insulation resin sheet was placed on theconductive circuitry layer of the second light transmissive supportivesubstrate so as to cover the entire conductive circuitry layer and lighttransmissive insulator, and six LED chips were laid out at apredetermined location on the second light transmissive insulation resinsheet. The six LED chips were each laid out in such a way that thesecond electrode was located at thesecond-light-transmissive-insulation-resin-sheet side. The first lighttransmissive insulation resin sheet and the first light transmissivesupportive substrate were laminated on the six LED chips. The firstlight transmissive insulation resin sheet was placed in such a way thatthe conductive circuitry layer of the first light transmissivesupportive substrate was located at thefirst-light-transmissive-insulation-resin-sheet side. The first lighttransmissive insulation resin sheet was formed in a shape that coveredthe entire conductive circuitry layer of the first light transmissivesupportive substrate and light transmissive insulator.

Next, a laminated body that had the second light transmissive supportivesubstrate, the second light transmissive insulation resin sheet, the LEDchips, the first light transmissive insulation resin sheet, and thefirst light transmissive supportive substrate laminated in this orderwas pre-pressed at a pressure of 0.1 MPa, and the air was drawn from thework space to accomplish a vacuum condition of 0.1 kPa. The laminatedbody was pressed at a pressure of 9.8 MPa under a vacuum condition of 5kPa while being heated at 120° C. The heating and pressurizing conditionwas maintained for 10 minutes to electrically connect the electrode ofthe LED chip to the conductive circuitry layer and to cause the firstand second light transmissive insulation resin sheets to be embeddedbetween the first light transmissive supportive substrate and the secondlight transmissive supportive substrate, and thus the light transmissiveinsulator was formed.

Subsequently, external wirings were connected to the conductivecircuitry layer, and thus 12 light emitting devices each having six LEDchips connected in series and emitting light when a current was suppliedfrom an external circuit were produced. In addition, as the firstcomparative example and the second comparative example, except that theLED chip which had no bump formed was utilized, 12 light emittingdevices through the same processes as first to fourteenth examples wereproduced for each comparative example. The obtained light emittingdevices were subjected to characteristics evaluation to be explainedlater.

The respective characteristics of the light emitting devices accordingto the first to fourteenth examples and first to second comparativeexamples were evaluated as follow. Six samples were prepared for each ofthe first to fourteenth examples and first to second comparativeexamples. As for the six samples of each example, a flex resistance testdefined in JIS C5016 (IEC249-1 and IEC326-2) 8.6 was carried out in anelectrically conducted condition. This flex resistance test was carriedout for all samples under an environment in which the temperature was35±2° C., the relative humidity was 60 to 70%, and the atmosphericpressure was 86 to 106 kPa. The six samples were flexed in such a waythat the LED chip string was moved toward the center of flexed part andthe second conductive circuitry layer was moved inwardly in a directionorthogonal to the laid-out direction of the LED chips, and the minimumflexure radius (minimum value of flexure radius still enabling a lightemission) of the sample flexed in the direction orthogonal to thelaid-out direction of the LED chips was examined.

First of all, plural kinds of measurement circular cylinders that had across-section in a true circular shape were prepared. Next, the obtainedlight emitting device was set to the circular cylinder in such a waythat the back surface to the light emitting surface of the LED chip wasin contact with the curved surface of the measurement circular cylinder.The light emitting device was actuated to emit light, and in thiscondition, the light emitting device was flexed by 180 degrees along thecurved surface of the measurement circular cylinder. This flex test wascarried out in the order from the measurement circular cylinder with thelargest radius to the measurement circular cylinder with the smallestradius, and the examination was made for up to which curvature radius ofthe measurement circular cylinder the light emitting condition was stillmaintained. Table 1 shows the results.

As is clear from table 1, it was confirmed that the light emittingdevices of the fifth example and the eighth to fourteenth examplesmaintained the light emitting condition even if the flex radius wasreduced in the flex resistance test.

The embodiments of the present disclosure have been explained above, butthe present disclosure is not limited to the above-explainedembodiments. For example, the conductive bump applied in the foregoingembodiments may be a wire bump formed using a wire bonder, or bumpsformed by electrolytic plating, non-electrolytic plating, inkjetprinting and calcining of an ink containing metal micro particle,printing of a paste containing metal micro particle, coating ballmounting, pellet mounting, vapor deposition sputtering, etc. Inaddition, the bump is not limited to those types, and various conductivebump like a lift-off bump is also applicable.

In addition, the conductive bump may be formed of a mixture of metalmicro particle with a resin. In this case, for example, a metal, such asa silver (Ag) or copper (Cu), or an alloy thereof may be mixed in athermosetting resin to obtain a paste, the droplets of the paste may beapplied to the electrode by ink jetting or needle dispensing, andsolidified by heating to form a conductive bump.

Several embodiments of the present disclosure have been explained, butthose embodiments are merely presented as examples, and are not intendedto limit the scope of the present disclosure. Those novel embodimentscan be carried out in other various forms, and various omissions,replacements, and modifications can be made thereto without departingfrom the scope of the present disclosure. Those embodiments and modifiedforms thereof should be within the scope of the present disclosure, andthe scope of the invention as recited in appended claims and theequivalent range thereto.

What is claimed is:
 1. A light emitting device comprising: a first lighttransmissive supportive substrate that comprises a first lighttransmissive insulator and a first conductive circuitry layer providedon a surface of the first light transmissive insulator; a second lighttransmissive supportive substrate which comprises a second lighttransmissive insulator, and which is disposed so as to have apredetermined gap from the first light transmissive supportivesubstrate; a light emitting diode which comprises a light emitting diodemain body, and first and second electrodes, the first electrodeelectrically connecting the light emitting diode main body to the firstconductive circuitry layer via a first conductive bump, the lightemitting diode is between the first light transmissive supportivesubstrate and the second light transmissive supportive substrate; and athird light transmissive insulator formed in a space between the firstlight transmissive supportive substrate and the second lighttransmissive supportive substrate, wherein the first light transmissivesupportive substrate, the second light transmissive supportive substrateand the third light transmissive insulator have flexibility, a height ofthe first conductive bump is a height at which the first electrode or asemiconductor layer of the light emitting diode main body does notcontact the first conductive circuitry layer when the light emittingdevice is bent with a radius of 50 mm, and the height of the firstconductive bump is in the range of from 5 μm to 50 μm.
 2. The lightemitting device according to claim 1, wherein a surface of the secondlight transmissive insulator faces the first conductive circuitry layer,the light emitting diode comprises the light emitting diode main body,the first electrode is provided on a surface of the light emitting diodemain body and a second electrode is provided on the surface of the lightemitting diode main body and is electrically connected to the firstconductive circuitry layer via a second conductive bump.
 3. The lightemitting device according to claim 1, wherein the second lighttransmissive supportive substrate comprises a second conductivecircuitry layer provided on a surface of the second light transmissiveinsulator, and the second conductive circuitry layer faces the firstconductive circuitry layer, the light emitting diode comprises a lightemitting diode main body, the first electrode provided on a surface ofthe light emitting diode main body and electrically connected to thefirst conductive circuitry layer via the first conductive bump, and thesecond electrode provided on an opposite surface of the light emittingdiode main body and electrically connected to the second conductivecircuitry layer.
 4. The light emitting device according to claim 2,wherein a ratio of B/A is in the range of from 0.2 to 0.7, where: A is adiameter of a surface of the first conductive bump in contact with thefirst electrode and B is the height of the first conductive bump, or Ais a diameter of a surface of the second conductive bump in contact withthe second electrode and B is a height of the second conductive bump. 5.The light emitting device according to claim 2, wherein the secondconductive bump has a height of equal to or higher than 5 μm and equalto or lower than 50 μm.
 6. The light emitting device according to claim2, wherein a contact area between the first conductive bump and thefirst electrode, and a contact area between the second conductive bumpand the second electrode are each equal to or larger than 100 μm² andequal to or smaller than 15000 μm².
 7. The light emitting deviceaccording to claim 2, wherein a material of the first conductive bump isany one of the following: gold; silver; copper; nickel; and an alloythereof.
 8. The light emitting device according to claim 2, wherein thematerial of the first conductive bump is any one of the following: gold;silver; copper; nickel; an Au-Sn alloy; and a nickel alloy.
 9. The lightemitting device according to claim 2, wherein the first conductive bumpis a mixture of metal microparticle with a resin.
 10. The light emittingdevice according to claim 2, wherein the first conductive bump has amelting-point temperature of equal to or higher than 180 ° C.
 11. Thelight emitting device according to claim 2, wherein the first conductivebump has a dynamic hardness of equal to or higher than 3 and equal to orlower than
 150. 12. The light emitting device according to claim 2,wherein at least one of an upper surface of the first conductive bumpand an upper surface of the second conductive is flat.
 13. The lightemitting device according to claim 2, wherein a ratio between a distancefrom a surface of the light emitting diode to a top of the firstconductive bump, and, a distance from a center of the first conductivebump to a most distant end of the light emitting diode is equal to orlarger than 0.120 and equal to or smaller than 0.400.
 14. The lightemitting device according to claim 2, wherein the first conductivecircuitry layer is concaved along the first conductive bump.
 15. Thelight emitting device according to claim 2, wherein the light emittingdiode is embedded in the third light transmissive insulator.
 16. Thelight emitting device according to claim 2, wherein the first electrodeand the first conductive circuitry layer do not directly contact witheach other, but the first conductive bump directly contacts the firstconductive circuitry layer.
 17. The light emitting device according toclaim 1, wherein a contact angle between a first surface of the firstelectrode and the first conductive bump is equal to or smaller than 135degrees.
 18. The light emitting device according to claim 1, wherein inthe first conductive circuitry layer, a portion in contact with thefirst conductive bump is recessed.
 19. The light emitting deviceaccording to claim 1, wherein the third light transmissive insulator isfilled between the first conductive circuitry layer and the first andsecond electrodes, and between the first conductive circuitry layer andthe semiconductor layer.
 20. A flexible light emitting devicecomprising: a first light transmissive substrate that comprises a firstlight transmissive insulator and a conductive layer on the first lighttransmissive insulator; a second light transmissive substrate thatcomprises a second light transmissive insulator, the second lighttransmissive substrate disposed with a gap from the first lighttransmissive substrate; a light emitting diode having a light emittingdiode body, and first and second electrodes, the first electrodeelectrically connecting the light emitting diode body to the conductivelayer via a conductive bump, the light emitting diode is located betweenthe first light transmissive substrate and the second light transmissivesubstrate; and a third light transmissive insulator formed in a spacebetween the first light transmissive substrate and the second lighttransmissive substrate, the third light transmissive insulator having athinner thickness than a height of the light emitting diode; wherein thefirst light transmissive substrate in contact with the third lighttransmissive insulator is formed in a curved shape inwardly from a partwhere the light emitting diode is laid out and toward a middle portionbetween an adjoining light emitting diode.
 21. The flexible lightemitting device according to claim 20, wherein the first lighttransmissive substrate pushes the conductive layer against the firstelectrode.
 22. The flexible light emitting device according to claim 20,wherein a height of the conductive bump is equal to or higher than 5 μmand equal to or lower than 50 μm.
 23. The flexible light emitting deviceaccording to claim 22, wherein the height of the conductive bump isequal to or higher than 20 μm and the flexible light emitting deviceexhibits a light emitting condition is maintained in a flex resistancetest, when the flexible light emitting device in a lighting state iswound about a circular cylinder having a 50mm radius.
 24. The flexiblelight emitting device according to claim 20, wherein the third lighttransmissive insulator is filled among the conductive layer, a sidesurface of the conductive bump and an upper surface of the lightemitting diode body.
 25. The flexible light emitting device according toclaim 20, wherein the conductive layer is concaved along the conductivebump.
 26. The flexible light emitting device according to claim 20,wherein a height of the conductive bump is equal to or higher than 20 μmand equal to or lower than 50 μm, and a ratio between a distance from asurface of the light emitting diode to a top of the conductive bump,and, a distance from a center of the conductive bump to a most distantend of the light emitting diode is equal to or larger than 0.12 andequal to or smaller than 0.40.
 27. A flexible light emitting devicecomprising: a first light transmissive substrate having a first lighttransmissive insulator and a conductive layer on the first lighttransmissive insulator; a second light transmissive substrate having asecond light transmissive insulator, disposed with a gap from the firstlight transmissive substrate; a light emitting diode having a lightemitting diode body, and first and second electrodes, the firstelectrode electrically connecting the light emitting diode body to theconductive layer via a conductive bump, the light emitting diode islocated between the first light transmissive substrate and the secondlight transmissive substrate; and a third light transmissive insulatorformed in a space between the first light transmissive substrate and thesecond light transmissive substrate; wherein a height of the conductivebump is equal to or higher than 20 μm and equal to or lower than 50 μm,and a ratio between a distance from a surface of the light emittingdiode to a top of the conductive bump, and, a distance from a center ofthe conductive bump to a most distant end of the light emitting diode isequal to or larger than 0.12 and equal to or smaller than 0.40.
 28. Theflexible light emitting device according to claim 27, wherein the heightof the conductive bump is equal to or higher than 30 μm.
 29. Theflexible light emitting device according to claim 27, wherein theflexible light emitting device exhibits a light emitting condition ismaintained in a flex resistance test, when the flexible light emittingdevice in a lighting state is wound about a circular cylinder having a50 mm radius.
 30. The flexible light emitting device according to claim28, wherein the flexible light emitting device exhibits a flexural testin terms of a lighting maintaining rate at least 6/6 at a bending radiusof 20 mm , when the flexible light emitting device in a lighting stateis wound about a circular cylinder a specified bending radius.
 31. Theflexible light emitting device according to claim 27, wherein the firstlight transmissive substrate in contact with the third lighttransmissive insulator is formed in a curved shape inwardly from a partwhere the light emitting diode is laid out and toward a middle portionbetween an adjoining light emitting diode.
 32. The flexible lightemitting device according to claim 27, wherein the third lighttransmissive insulator has a thinner thickness than a height of thelight emitting diode.
 33. The flexible light emitting device accordingto claim 31, wherein the third light transmissive insulator is filledamong the conductive layer, a side surface of the conductive bump and anupper surface of the light emitting diode body.
 34. The flexible lightemitting device according to claim 31, wherein the conductive layer isconcaved along the conductive bump.